This invention relates to rack entry vehicles, and more particularly relates to apparatus for communicating information between a rack entry vehicle and a reference station.
There is a need for an accurate and reliable means of communicating information between a reference station and a movable vehicle. One field in which the need is acute is automatic storage systems. Such systems normally contain a large number of rows of racks on which loads are stored. The loads are normally retrieved by an unattended vehicle which moves on tracks between the rows of goods. The vehicle may be carried on a crane which moves up and down aisles between the rows. In order to effectively store and retrieve goods, the vehicle must be able to communicate with the aisle crane.
In the past, a communication link between the vehicle and the crane has taken the form of an umbilical cord or radio frequency communications. Either one of these approaches has disadvantages. The umbilical cord necessitates cumbersome and expensive cord winding equipment. Radio communications require approval by the Federal Communications Commission and careful shielding designed to provide protection from the environment and protection from interference by other radio transmitters in the area. Since the racks are grounded, a radio signal is severely attenuated as it propagates through the warehouse. The attenuation necessitates increased transmitter power which normally is discouraged by the FCC. If a low power transmitter is used, expensive receivers are required. In the event multiple vehicles are operated simultaneously, multiple carrier frequencies must be utilized in order to prevent interference between vehicles. This requirement substantially increases the cost of the overall system.
As a result, it is an object of the present invention to provide an improved communication system between a movable vehicle and a reference station.
It is another object to provide a system of the foregoing type suitable for use by a rack entry vehicle operating in a steel rack warehouse.
Yet another object is to provide a system of the foregoing type in which optical radiation, such as infrared radiation, is used for the communicating medium.
Still another object is to provide a system of the foregoing type in which the optical radiation is pulsed in order to encode the information transmitted between the vehicle and the station.
Still another object of the present invention is to provide a system of the foregoing type in which information is processed in parallel form, but is transmitted and received in the serial form.